Malå Imaging Radar Arrays (MIRA)
As opposed to normal multi-channel systems, the MIRA system enables fast and easy, true, 3-D data acquisition. From a user perspective this means that large areas can be mapped without loss of information and that the method is suitable for almost any kind of, shallow, subsurface investigation, i.e. targets with arbitrary shape, layers and linear objects are mapped equally well.
The MIRA system consists of several separate transmitter and receiver antennas combined into one single antenna array unit. In operation, the antenna array is tracked and positioned by a robotic (self-tracking) total station or a RTK GPS for precise positioning. This give several parallel profiles exactly positioned at the same time, resulting in a seamless 3D picture of the subsurface, with a high-resolution of subsurface features both in horizontal and vertical direction.
AUSTRALIAN APPLICATIONS: In Australia the MIRA system would typically be used for high-level service locating, road mapping and archeological applications. The underground utility infrastructure system in Australia is relatively poorly documented and the MIRA system enables organisations to quickly generate a 3D map of the utilities. Not only are the utilities located efficiently and with maximum detection rate, accurate their location and depth is also recorded for future reference.
The system is suited for industry leading private organisations operating on the highest level and who are industry leading within their field. Some training is required and dedicated personnel for its operation is recommended.
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The MIRA systems represent a completely reworked, revolutionary new generation of GPR equipment, patents pending. At this time, MIRA systems are not available in the United States due to FCC regulations.
Hardware
By adding the array option to a modified ProEx, a full-blown array control unit is formed, with up to 31 recording channels (in what we call normal configuration) possible. This control unit will have the functionality necessary for array operations, which in Mala terminology is equivalent to:
Ability to transmit pulses from any transmitter to any receiver at any time, a necessary functionality in dense array designs.
No multiplexing, meaning the system will always run at full speed, regardless if the whole array is active or only a single channel (i.e. traditional single channel GPR)
Array antennas are available as 200, 400 and 1.3GHz separate receiver and transmitter elements. They are designed to allow very dense arrangements and could also be arranged according to the customer needs, to allow for polarimetric studies etc. All array antennas are carefully tuned to near identical signatures, a requirement necessary for array operation.
Optionally, for standard configuration, MALÅ provides housing for the antenna arrays with premounted arrangements for a vehicle. The array boxes are equipped with colour marking devices for easier control of area coverage. Should a client choose to supply the data acquisition laptop, the positioning system and the vehicle on their own, MALÅ will provide the necessary specifications.
Software
Data acquisition is done by means of a, preferable ruggedized, laptop, running Microsoft Windows XP OS. The acquisition software allows precise quality control as well as automatic tagging of positioning information during acquisition.
In brief, the processing and interpretation software performs processing, interpolation and 3D migration of the acquired data, followed by interactive interpretation of the features observed. One important feature, for overall efficiency, is the seamless integration of positioning information, allowing arbitrary number of array swats to be integrated into a seamless data set. The results can easily be printed or exported as GIS compatible formats such as, geo-referenced TIFF- of DXT-files.
